Waterproof sheet and waterproof treatment

ABSTRACT

A waterproof sheet comprising a rubber base and a pressure-sensitive adhesive layer of silicone resin or gel thereon is applicable to the boundary between an outdoor tank and a concrete pedestal. The waterproof sheet maintains waterproofness over a long period of time and is in long-term service without degradation of physical properties.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under U.S.C. §119(a) onPatent Application No. 2011-077757 filed in Japan on Mar. 31, 2011, theentire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to a waterproof sheet and a waterproof treatingmethod, which are effectively applied to an outdoor tank resting on aconcrete pedestal, typically a large volume tank resting on a concretepedestal as often found in oil refinery plants, for preventing rainwaterfrom entering the boundary between the bottom side of the tank and theconcrete pedestal.

BACKGROUND ART

One problem associated with an outdoor tank resting on a concretepedestal, typically a large volume tank resting on a concrete pedestalas often found in oil refinery plants, is that rainwater enters theboundary between the bottom side of the tank and the concrete pedestal.The problem is addressed by covering the boundary between the tankbottom and the concrete pedestal with a butyl-based pressure-sensitiveadhesive rubber sheet for preventing the entry of rainwater. However,since the butyl-based PSA rubber sheet is poor in weather resistance,heat resistance and freeze resistance, it fails to prevent the entry ofrainwater over a long period of time, allowing rust generation at thebottom of the outdoor tank, with potential tank failure.

CITATION LIST

-   Patent Document 1: JP-A H04-005336-   Patent Document 2: JP-A H08-198384-   Patent Document 3: JP-A 2000-064068-   Patent Document 4: JP 4076673

SUMMARY OF INVENTION

An object of the invention is to provide a waterproof sheet which iseffectively applied to the boundary between an outdoor tank and aconcrete pedestal for maintaining waterproofness over a long period oftime without degradation of physical properties, and a waterprooftreating method.

In one aspect, the invention provides a waterproof sheet comprising arubber base and a pressure-sensitive adhesive (PSA) layer disposedthereon, the adhesive layer comprising a pressure-sensitive adhesivesilicone resin or gel.

In a preferred embodiment, the rubber base is formed of silicone rubberhaving a hardness of 10 to 90 on JIS A scale.

In a preferred embodiment, the pressure-sensitive adhesive layer isformed of a cured product of an addition cure silicone rubbercomposition, the addition cure silicone rubber composition comprising

(A) 20 to 100 parts by weight of an organopolysiloxane containing atleast two silicon-bonded alkenyl groups in a molecule, having theaverage compositional formula (1):

R¹ _(a)SiO_((4-a)/2)  (1)

wherein R¹ is each independently a substituted or unsubstitutedmonovalent hydrocarbon group of 1 to 10 carbon atoms, and a is apositive number of 1.5 to 2.8,

(B) 0 to 80 parts by weight of a resinous copolymer predominantlycomprising R₃SiO_(1/2) units and SiO₂ units, a molar ratio ofR₃SiO_(1/2) units to SiO₂ units being in a range of 0.5 to 1.5, whereinR is a substituted or unsubstituted monovalent hydrocarbon group, and Rcontains alkenyl in a total amount of at least 0.0001 mol/g, the totalamount of components (A) and (B) being 100 parts by weight,

(D) an organohydrogenpolysiloxane containing at least two silicon-bondedhydrogen atoms in a molecule in an amount of 0.5 to 30 parts by weightrelative to 100 parts by weight of components (A) and (B) combined, theamount being such that a molar ratio of silicon-bonded hydrogen incomponent (D) to silicon-bonded alkenyl group in components (A) and (B)is in a range of 0.2 to 1.5, and

(E) a catalytic amount of an addition reaction catalyst, the curedproduct having surface pressure-sensitive adhesion.

The addition cure silicone rubber composition may further comprise (C) aresinous copolymer predominantly comprising R′₃SiO_(1/2) units and SiO₂units, a molar ratio of R′₃SiO_(1/2) units to SiO₂ units being in arange of 0.5 to 1.5, wherein R′ is a substituted or unsubstitutedmonovalent hydrocarbon group, and R′ does not contain or containsalkenyl in a total amount of less than 0.0001 mol/g, in an amount of 0to 400 parts by weight relative to 100 parts by weight of components (A)and (B) combined, the amount being such that a molar ratio ofsilicon-bonded hydrogen in component (D) to silicon-bonded alkenyl groupin components (A), (B), and (C) is in a range of 0.32 to 0.75 whencomponent (C) contains alkenyl.

In a preferred embodiment, the pressure-sensitive adhesive layer has ahardness which is lower than that of the rubber base and in a range of 1to 60 on Asker C hardness scale.

In a preferred embodiment, the pressure-sensitive adhesive layer has abond strength of 0.5 to 10 N/25 mm to glass.

In a preferred embodiment, the rubber base has a thickness of 0.2 to 5mm and the pressure-sensitive adhesive layer has a thickness of 0.3 to 3mm.

Most often, the waterproof sheet is applied to the boundary between anoutdoor tank and a concrete pedestal for waterproof treating the outdoortank.

In another aspect, the invention provides a method of waterprooftreating an outdoor tank rested on a concrete pedestal, comprisingapplying the waterproof sheet defined above across an externally exposedboundary between the tank and the pedestal, with the pressure-sensitiveadhesive layer of the waterproof sheet being attached to the tank andthe pedestal.

In this case, the pressure-sensitive adhesive layer of the waterproofsheet can be directly attached to the tank and the pedestal without aprimer.

A sealant may be applied around the waterproof sheet. More particularly,the sealant is applied along the outer periphery of thepressure-sensitive adhesive layer of the waterproof sheet to form asealing layer at the outer periphery of the pressure-sensitive adhesivelayer. The sealant is typically a silicone sealant.

Throughout the disclosure, the term “pressure-sensitive adhesive” isabbreviated as PSA.

Advantageous Effects of Invention

Since the waterproof sheet maintains waterproofness over a long periodof time, it is in long-term service without degradation of physicalproperties. The outdoor tank treating method ensures that the outdoortank is treated waterproof at the bottom side in a simple manner.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a cross-sectional view of a waterproof sheet of the invention.

FIG. 2 is a schematic cross-sectional view of an outdoor tank resting ona pedestal.

FIG. 3 is an enlarged view of circle A in FIG. 2.

FIG. 4 is a schematic cross-sectional view of a waterproof sheetcovering the boundary between an outdoor tank and a concrete pedestal.

FIG. 5 is a plan view of the waterproof sheet of FIG. 4.

FIG. 6 is a schematic cross-sectional view of the waterproof sheet ofFIG. 4 on which a sealing layer is formed.

FIG. 7 is a plan view of the waterproof sheet and sealing layer of FIG.6, assuming that the waterproof sheet is transparent.

DESCRIPTION OF EMBODIMENTS

Referring to FIG. 1, a waterproof sheet 10 is illustrated as comprisinga rubber base 1 and a PSA layer 2 disposed on one surface of rubber base1. Typically the PSA layer 2 is overlaid with a cover film 3 in areleasable manner. On use, the cover film 3 is peeled, and the adhesivelayer 2 is attached to the desired member.

The rubber base is preferably made of silicone rubber because of itsheat resistance, weather resistance and freeze resistance. The siliconerubber used herein is not particularly limited, and any of siliconerubbers obtained by curing prior art well-known silicone rubbercompositions may be used. It is preferred from the standpoints ofelasticity and rubber strength to use a silicone rubber having ahardness of 10 to 90, more preferably 20 to 80, and even more preferablyat least 25, especially at least 40 and up to 80, especially up to 75 asmeasured by a type A Durometer according to JIS K6249. Rubber with a JISA hardness of less than 10 may have poor strength whereas rubber with ahardness in excess of 90 may have poor elasticity.

The silicone rubber composition used herein may be of any cure typealthough the preferred silicone rubber composition may be of eitheraddition (hydrosilylation) reaction cure type or organic peroxide curetype. The silicone rubber composition of addition reaction cure type mayhave a well-known formulation, typically comprising an alkenyl-bearingorganopolysiloxane containing at least two alkenyl groups (typicallyvinyl) in a molecule, an organohydrogenpolysiloxane containing at leasttwo, preferably at least three SiH groups (typically in an amount togive a molar ratio of SiH group to alkenyl group of 0.5 to 4), and aplatinum group metal-based addition reaction catalyst, typicallyplatinum or a platinum compound (typically in an amount of 1 to 1,000ppm based on the alkenyl-bearing organopolysiloxane). The siliconerubber composition of organic peroxide cure type may also have awell-known formulation, typically comprising an organopolysiloxanecontaining at least two alkenyl groups in a molecule, and a curingamount (typically 1 to 10 parts by weight per 100 parts by weight of theorganopolysiloxane) of an organic peroxide as curing agent.

As the silicone rubber composition, any commercially available productsmay be used. For example, commercially available silicone rubbercompositions of the addition reaction cure type include KE-1935A/B,KE-1950-60A/B, and KEG-2000-40A/B from Shin-Etsu Chemical Co., Ltd. andcommercially available silicone rubber compositions of the organicperoxide cure type include KE-551-U, KE-571-U, KE-1571-U, and KE-951-Ufrom Shin-Etsu Chemical Co., Ltd.

The PSA layer is formed of a silicone resin or gel havingpressure-sensitive adhesion. In particular, an addition cure compositionmay be used to form a layer having sufficient pressure-sensitiveadhesion to tightly adhere and fixedly attach to the base and variousmembers while maintaining a certain rubber hardness and rubber strength.

In a preferred embodiment, the PSA layer is formed of a cured product ofan addition cure silicone rubber composition comprising the followingcomponents:

(A) an organopolysiloxane containing at least two silicon-bonded alkenylgroups in a molecule,

(B) a resinous copolymer predominantly comprising R₃SiO_(1/2) units andSiO₂ units wherein R is a substituted or unsubstituted monovalenthydrocarbon group and contains alkenyl,

(D) an organohydrogenpolysiloxane containing at least two silicon-bondedhydrogen atoms (i.e., SiH groups) in a molecule, and

(E) an addition reaction catalyst, the cured product having surfacepressure-sensitive adhesion.

The addition cure silicone rubber composition may further comprise (C) aresinous copolymer predominantly comprising R′₃SiO_(1/2) units and SiO₂units wherein R′ is a substituted or unsubstituted monovalenthydrocarbon group and does not contain or contains alkenyl in a lessamount than the alkenyl content of component (B).

Component (A) is an organopolysiloxane containing, on average, at leasttwo alkenyl groups in a molecule. The organopolysiloxane (A) has theaverage compositional formula (1).

R¹ _(a)SiO_((4-a)/2)  (1)

Herein R¹ is each independently a substituted or unsubstitutedmonovalent hydrocarbon group of 1 to 10 carbon atoms, preferably 1 to 8carbon atoms, and a is a positive number of 1.5 to 2.8, preferably 1.8to 2.5, and more preferably 1.95 to 2.05. Examples of the silicon-bondedsubstituted or unsubstituted monovalent hydrocarbon group represented byR¹ include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl,isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyland decyl, aryl groups such as phenyl, tolyl, xylyl, and naphthyl,aralkyl groups such as benzyl, phenylethyl, and phenylpropyl, alkenylgroups such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl,cyclohexenyl, and octenyl, and substituted forms of the foregoing inwhich some or all hydrogen atoms are substituted by halogen atoms (e.g.,fluorine, bromine or chlorine), cyano or other radicals, such aschloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl.Preferably methyl accounts for at least 90 mol % of the entire R¹.

At least two of R¹ must be alkenyl groups, preferably of 2 to 8 carbonatoms, more preferably 2 to 6 carbon atoms.

The alkenyl content is preferably 0.0001 to 20 mol %, more preferably0.001 to 10 mol %, and even more preferably 0.01 to mol % of the entireorganic groups R¹ (i.e., substituted or unsubstituted monovalenthydrocarbon groups as illustrated above). The alkenyl group may beattached to the silicon atom at the end of the molecular chain, or asilicon atom midway the molecular chain, or both. It is preferred thatthe organopolysiloxane have at least alkenyl groups attached to thesilicon atoms at both ends of the molecular chain.

While the degree of polymerization is not particularly limited, theorganopolysiloxane used herein may be either liquid or gum-like at roomtemperature. Typically the organopolysiloxane has an average degree ofpolymerization of 50 to 20,000, preferably 100 to 10,000, and morepreferably 100 to 2,000, as measured by gel permeation chromatography(GPC) versus polystyrene standards. With respect to the structure, theorganopolysiloxane generally has a straight chain structure whosebackbone is composed of recurring diorganosiloxane (R¹ ₂SiO_(2/2)) unitsand which is capped with a triorganosiloxy (R¹ ₃SiO_(1/2)) orhydroxydiorganosiloxy ((HO)R¹ ₂SiO_(1/2)) group at either end of themolecular chain. However, it may have in part a branched or cyclicstructure.

Component (B) is a resinous copolymer predominantly comprisingR₃SiO_(1/2) units and SiO₂ units. The resinous copolymer is a copolymerhaving three-dimensional network structure. Herein R is a substituted orunsubstituted monovalent hydrocarbon group, preferably of 1 to 10 carbonatoms, more preferably 1 to 8 carbon atoms. Examples of the monovalenthydrocarbon group represented by R include alkyl groups such as methyl,ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl,neopentyl, hexyl, cyclohexyl, octyl, nonyl and decyl, aryl groups suchas phenyl, tolyl, xylyl, and naphthyl, aralkyl groups such as benzyl,phenylethyl, and phenylpropyl, alkenyl groups such as vinyl, allyl,propenyl, isopropenyl, butenyl, hexenyl, cyclohexenyl, and octenyl, andsubstituted forms of the foregoing in which some or all hydrogen atomsare substituted by halogen atoms (e.g., fluorine, bromine or chlorine),cyano or other radicals, such as chloromethyl, chloropropyl, bromoethyl,trifluoropropyl, and cyanoethyl.

The resinous copolymer (B) may consist of R₃SiO_(1/2) units and SiO₂units, or may optionally further contain R₂SiO units and RSiO_(3/2)units wherein R is as defined above, in a total amount of up to 50%,preferably up to 40% of the total weight of the copolymer. A molar ratioof R₃SiO_(1/2) units to SiO₂ units, [R₃SiO_(1/2)/SiO₂], is in a range of0.5/1 to 1.5/1, preferably 0.5 to 1.3. If the molar ratio is outside therange, rubber hardness and strength fall outside the desired ranges.Further, the resinous copolymer (B) should preferably have at least twoalkenyl groups in a molecule. The content of alkenyl group is at least0.0001 mol/g, preferably 0.0001 to 0.003 mol/g, and more preferably0.0002 to 0.002 mol/g. If the alkenyl content is less than 0.0001 mol/g,no sufficient rubber physical properties are available. An alkenylcontent of more than 0.003 mol/g may lead to too high rubber hardnessand low bond strength.

The resinous copolymer (B) may be either a liquid one having fluidity atroom temperature (25° C.), for example, having a viscosity of at least10 mPa-s, preferably at least 50 mPa-s, or a solid one having nofluidity. The resinous copolymer may be prepared from hydrolysis ofchlorosilanes or alkoxysilanes by a technique well known in the art.

Components (A) and (B) are compounded in such amounts that component (A)is 20 to 100 parts by weight, preferably 30 to 90 parts by weight, andcomponent (B) is 0 to 80 parts by weight, preferably 10 to 70 parts byweight, provided that the total amount of components (A) and (B) is 100parts by weight. If the amount of component (A) is too small, thecomposition loses rubber elasticity and becomes brittle. If the amountof component (A) is excessive, pressure-sensitive adhesion and strengthbecome insufficient. If the amount of component (B) is excessive,pressure-sensitive adhesion lowers and rubber physical properties areconsiderably degraded.

In addition to the resinous copolymer as component (B), another resinouscopolymer may be compounded in the composition as component (C) ifnecessary. Component (C) is a resinous copolymer predominantlycomprising R′₃SiO_(1/2) units and SiO₂ units, the resinous copolymerbeing a copolymer having three-dimensional network structure. Herein R′is a substituted or unsubstituted monovalent hydrocarbon group,preferably of 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms.Examples of the monovalent hydrocarbon group represented by R′ includealkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl anddecyl, aryl groups such as phenyl, tolyl, xylyl, and naphthyl, aralkylgroups such as benzyl, phenylethyl, and phenylpropyl, alkenyl groupssuch as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl,cyclohexenyl, and octenyl, and substituted forms of the foregoing inwhich some or all hydrogen atoms are substituted by halogen atoms (e.g.,fluorine, bromine or chlorine), cyano or other radicals, such aschloromethyl, chloropropyl, bromoethyl, trifluoropropyl, and cyanoethyl.

The resinous copolymer (C) may consist of R′₃SiO_(1/2) units and SiO₂units, or may optionally further contain R′₂SiO units and R′SiO_(3/2)units wherein R′ is as defined above, in a total amount of up to 50%,preferably up to 40% of the total weight of the copolymer. A molar ratioof R′₃SiO_(1/2) units to SiO₂ units, [R′₃SiO_(1/2)/SiO₂], is in a rangeof 0.5/1 to 1.5/1, preferably 0.5 to 1.3. If the molar ratio is outsidethe range, pressure-sensitive adhesion becomes lower.

The resinous copolymer (C) should have an alkenyl content of less than0.0001 mol/g (i.e., 0 to 0.0001 mol/g), preferably up to 0.00005 mol/g(i.e., 0 to 0.00005 mol/g), and more preferably be free of alkenyl. Analkenyl content in excess of 0.0001 mol/g adversely affectspressure-sensitive adhesion.

The resinous copolymer (C) may be either a liquid one having fluidity atroom temperature (25° C.) or a solid one having no fluidity. A resinouscopolymer which is solid at room temperature is preferable forpressure-sensitive adhesion of a cured product. The resinous copolymermay be prepared from hydrolysis of chlorosilanes or alkoxysilanes by atechnique well known in the art.

The resinous copolymer (C) may be compounded in an amount of 0 to 400parts by weight, preferably 0 to 300 parts by weight relative to 100parts by weight of components (A) and (B) combined. If component (C) isexcessive, pressure-sensitive adhesion and rubber physical propertiesmay become poor.

It is also preferred from the standpoints of rubber physical propertiesand pressure-sensitive adhesion that the total content of alkenyl groupsavailable from the resinous copolymers as components (B) and (C) be0.00001 to 0.002 mol/g, more preferably 0.00005 to 0.001 mol/g.

Component (D) is an organohydrogenpolysiloxane containing at least two,preferably at least three silicon-bonded hydrogen atoms (i.e., SiHgroups) in a molecule. It serves as a curing agent for curing thecomposition in that SiH groups in the molecule undergo hydrosilylation(or addition) reaction with silicon-bonded alkenyl groups in components(A), (B) and (C) to form crosslinks. Preferably theorganohydrogenpolysiloxane (C) has at least two (typically 2 to 200),more preferably 3 to 100, and even more preferably 3 to 50silicon-bonded hydrogen atoms in a molecule, and is represented by theaverage compositional formula (2):

R² _(b)H_(c)SiO_((4-b-c)/2)  (2)

wherein R² is a substituted or unsubstituted monovalent hydrocarbongroup of 1 to 10 carbon atoms, b is a positive number of 0.7 to 2.1, cis a positive number of 0.001 to 1.0, and b+c is 0.8 to 3.0. Themonovalent hydrocarbon groups of R² are as exemplified for R¹ andpreferably free of aliphatic unsaturation. Preferably, b is a positivenumber of 0.8 to 2.0, c is a positive number of 0.01 to 1.0, and b+c is1.0 to 2.5. The organohydrogenpolysiloxane has a molecular structurewhich may be linear, cyclic, branched or three-dimensional network. Thepreferred organohydrogenpolysiloxane is liquid at room temperature (25°C.) and has a number of silicon atoms (or degree of polymerization) ofabout 2 to about 300, more preferably about 4 to about 150. The hydrogenatom may be bonded to a silicon atom at the end or an intermediate ofthe molecular chain or both.

Instead of or in addition to the organohydrogenpolysiloxane havingformula (2), a resinous copolymer predominantly comprising R″₂HSiO_(1/2)units and SiO₂ units, or a resinous copolymer predominantly comprisingR″₂HSiO_(1/2) units, R″₃SiO_(1/2) units, and SiO₂ units may be used.Herein R″ is a substituted or unsubstituted monovalent hydrocarbongroup, which is as exemplified above for R′, and preferably free ofalkenyl. This resinous copolymer may consist of R″₂HSiO_(1/2) units andSiO₂ units, or R″₂HSiO_(1/2) units, R″₃SiO_(1/2) units, and SiO₂ units,and may optionally further contain R″HSiO_(2/2) units, R″₂SiO_(2/2)units, HSiO_(3/2) units, and R″SiO_(3/2) units in a total amount of upto 50%, preferably up to 40% of the total weight of the copolymer. Amolar ratio of R″₂HSiO_(1/2) and R″₃SiO_(1/2) units to SiO₂ units,[(R″₂HSiO_(1/2)+R″₃SiO_(1/2))/SiO₂] is preferably 0.5/1 to 1.5/1, morepreferably 0.5 to 1.3.

Examples of the organohydrogenpolysiloxane (D) include, but are notlimited to, trimethylsiloxy-endcapped methylhydrogenpolysiloxane,trimethylsiloxy-endcapped dimethylsiloxane-methylhydrogensiloxanecopolymers, dimethylhydrogensiloxy-endcapped dimethylpolysiloxane,dimethylhydrogensiloxy-endcapped dimethylsiloxane-methylhydrogensiloxanecopolymers, trimethylsiloxy-endcappedmethylhydrogensiloxane-diphenylsiloxane copolymers,trimethylsiloxy-endcappedmethylhydrogensiloxane-diphenylsiloxane-dimethylsiloxane copolymers,copolymers of (CH₃)₂HSiO_(1/2) units and SiO_(4/2) units, and copolymersof (CH₃)₂HSiO_(1/2) units, SiO_(4/2) units, and (C₆H₅)SiO_(3/2) units.As used herein and throughout the disclosure, the term “endcapped” meansthat a compound is capped at both ends with the indicated group unlessotherwise stated.

The organohydrogenpolysiloxane as component (D) is blended in an amountof 0.5 to 30 parts, preferably 0.6 to 20 parts by weight per 100 partsby weight of components (A) and (B) combined. Outside the range, rubberstrength is lost. Also preferably the organohydrogenpolysiloxane (D) isblended in such an amount that a molar ratio of SiH groups in component(D) to silicon-bonded alkenyl groups in components (A), (B) and (C) mayrange from 0.2 to 1.5, more preferably from 0.25 to 1.2, and even morepreferably from 0.3 to 0.9.

Component (E) is an addition reaction catalyst. Suitable catalystsinclude platinum based catalysts such as platinum black, platinicchloride, chloroplatinic acid, reaction products of chloroplatinic acidwith monohydric alcohols, complexes of chloroplatinic acid with olefins,complexes of chloroplatinic acid with vinylsiloxanes, and platinumbisacetoacetate; palladium based catalysts, and rhodium based catalysts.The addition reaction catalyst may be used in a catalytic amount, andtypically in such an amount to provide 0.5 to 1,000 ppm, more preferably1 to 500 ppm of platinum group metal based on the total weight ofcomponents (A), (B), and (C).

In a preferred embodiment, the PSA layer has a hardness which is lowerthan that of the rubber base and in a range of 1 to 60, more preferably2 to 55, and even more preferably 2 to 40 on Asker C hardness scale. AnAsker C hardness of less than 1 may lead to a poor rubber strengthwhereas an Asker C hardness in excess of 60 may lead to a loss ofpressure-sensitive adhesion.

Also in a preferred embodiment, the PSA layer has a bond strength of 0.5to 10 N/25 mm, more preferably 0.7 to 8 N/25 mm, when tested accordingto JIS Z0237 by pressure bonding the layer to glass (FL2.0, by NipponSheet Glass Co., Ltd.) and peeling at a peel rate of 300 mm/min and anangle of 180°. With a bond strength of less than 0.5 N/25 mm, when thePSA layer is attached to a certain member, the adhesive force thereto islow, giving rise to an attachment problem. A bond strength of more than10 N/25 mm may deprive the layer of rework and re-attachmentcapabilities.

In addition to the components mentioned above, the rubber base-formingcomposition and the PSA layer-forming composition may further compriseoptional components. Suitable components include fillers such as fumedsilica, precipitated silica, ground quartz, diatomaceous earth, andcalcium carbonate, electroconductive agents such as carbon black,conductive zinc white, and metal powders, and heat resistant agents suchas iron oxide and cerium oxide. Also useful are hydrosilylation reactionregulators such as nitrogen-containing compounds, acetylene compounds,phosphorus compounds, carboxylates, tin compounds, mercury compounds,and sulfur compounds, internal parting agents such as dimethylsiliconeoil, tackifiers, and thixotropic agents.

The rubber base typically has a thickness of 0.2 to 5 mm, preferably 0.5to 3 mm. A thickness of less than 0.2 mm may fail to take advantage ofsheet elasticity whereas a thickness in excess of 5 mm leads to anincreased weight, adversely affects attachment and is costly. The PSAlayer preferably has a thickness of 0.3 to 3 mm, more preferably 0.5 to2 mm. A PSA layer of less than 0.3 mm, when applied to a member, mayfail to accommodate surface irregularities of the member. A PSA layer ofmore than 3 mm may give rise to rubber failure because the rubberstrength at the attachment interface depends on the PSA layer.

The waterproof sheet of the invention is prepared by first forming arubber base. The rubber base may be formed as a single layer using asuitable rubber composition, typically silicone rubber composition, oras a composite layer with a layer of metals or various resins. Forexample, a sheet is directly formed by compression molding, casting,injection molding or the like; a sheet is formed on a metal substrate,resin substrate or resin film by insert molding; or a rubber sheetintegrated with another substrate is formed by dipping, coating,calendering, screen printing or the like. Of these techniques,calendering may be advantageously used.

Next, the rubber base is overlaid with the PSA layer. In one procedure,the rubber base composition is cured into a rubber base before the PSAlayer is formed thereon. In an alternative procedure, the rubber basecomposition is calendered or sheeted onto a film such as polyethyleneterephthalate (PET), and the PSA composition is deposited on theunvulcanized rubber base composition.

The PSA composition is deposited on the rubber base layer to form alaminate sheet by a suitable technique such as dipping, coating orscreen printing. Of these techniques, a layer may be advantageouslyformed by coating. The coating is preferably cured at a temperature of80 to 250° C. for 10 seconds to 1 hour. This may be followed bypost-curing at 120° C. to 250° C. for 1 to 100 hours for the purpose ofremoving a lower molecular weight siloxane fraction.

Referring to FIG. 1, a waterproof sheet 10 generally includes a rubberbase 1, a PSA layer 2 disposed on rubber base 1, and a cover film 3 suchas polyethylene terephthalate (PET) sheet lying on PSA layer 2 in areleasable manner. On use, the cover film 3 is peeled, and the PSA layer2 is attached to the desired member.

The waterproof sheet may be applied to the boundary between an outdoortank at its bottom and a concrete pedestal for the purpose of preventingentry of rainwater. Referring to FIGS. 2 to 7, one exemplary method isdescribed. FIG. 2 shows an outdoor tank 30 of steel resting on andsupported by a concrete pedestal 20. The outdoor tank 30 is intended tocontain a feedstock such as petroleum oils, asphalt, and gases. The tank30 is generally cylindrical, has a diameter of 10 to 80 meters and aheight of 10 to 50 meters, and is rested on the concrete pedestal 20 onthe ground depicted at 21. FIG. 3 is an enlarged view of circle A inFIG. 2. A boundary 40 is defined between the outdoor tank 30 near itsbottom and the concrete pedestal 20 and exposed to the exterior, and sorainwater may enter the boundary 40. On rainwater entry, the tank 30will rust. As shown in FIGS. 4 and 5, the waterproof sheet 10 is appliedacross the externally exposed boundary 40. Specifically, the waterproofsheet 10 is applied by peeling the cover film 3 therefrom, and attachingthe sheet so as to bring the PSA layer 2 in contact with the surfaces oftank 30 and pedestal 20 and to cover the boundary 40. More specifically,a plurality of waterproof sheets 10 are circumferentially arranged onthe boundary 40 as viewed in the plan view of FIG. 5. Furtherpreferably, a sealant is applied around the waterproof sheet 10. Asshown in FIGS. 6 and 7, a sealant 50 is applied along the outerperiphery of each waterproof sheet 10. Notably the sealant 50 alsoserves to bond the waterproof sheet 10 to the tank 30 and pedestal 20.The method employed to this end is, as shown in FIG. 6, by turning up anouter periphery portion of each waterproof sheet 10 so that the outerperiphery portion is slightly spaced apart from pedestal 20 or tank 30and feeding a sealant 50 into the gap between sheet 10 and pedestal 20or tank 30 for forming a sealing layer 50 along the outer periphery ofeach waterproof sheet 10. The sealant may be additionally applied so asto fill the space between tank 30 and the edge of sheet 10 as shown inFIGS. 6 and 7.

The sealant used herein is not particularly limited. Any of well-knownsilicone, polysulfide and polyurethane base sealants may be used, withthe silicone base sealants being preferred for affinity to thewaterproof sheet materials. Suitable sealants are commerciallyavailable. For example, silicone base sealants are commerciallyavailable as Sealant Master 300, Sealant 70 and Sealant 701 fromShin-Etsu Chemical Co., Ltd.

The waterproof sheet of the invention can be applied to the desiredmember without a need for primer, which leads to a substantial saving ofthe construction time.

With respect to the tanks installed in refinery and other plants, it islegally required to mount a rainwater-proofing means at thetank-pedestal junction (commonly known as annular plate) between thetank at its bottom and the tank-supporting pedestal. The water-proofingmeans is most commonly an array of butyl rubber sheets. However, whenthe member surface is wetted under the environment where water dropletsare condensed due to a weather temperature difference or a very highhumidity resulting from rain and snow, the butyl rubber sheets cannot beapplied until the member surface is dried. The primer-less applicationability of the waterproof sheet of the invention ensures that even whenthe member surface is wet, the sheet can be applied to the membersurface simply after the member surface is wiped with fabrics or wastes.Application of the waterproof sheet can be started immediately after theweather becomes good.

In general, the oil or hazardous stock-containing large-volume tanksinstalled in refinery and other plants must be inspected for safetymanagement every several years, as prescribed in the Fire Service Act ofJapan, for example. On such inspection, the rainwater-proofing meansmust be detached before the junction can be observed. Since thecurrently used butyl rubber sheets, sealants, and other waterproofsheets have been applied using primers, it is difficult to detach thesesheets to see the underneath structure. Since the waterproof sheet ofthe invention exerts the waterproof function by virtue ofpressure-sensitive adhesion, the sheet can be readily detached justafter the securing sealant at the edge of the sheet is removed,whereupon the underneath structure is inspected. By virtue ofpressure-sensitive adhesion, the waterproof sheet of the invention canbe attached in place again to exert the waterproof function.

Example

Examples are given below by way of illustration and not by way oflimitation. All parts and % are by weight.

Example 1

A rubber base layer was formed from a transparent uncrosslinkeddimethylsilicone rubber compound. Specifically, a dimethylsiliconerubber composition was prepared by providing 100 parts of a millabledimethylsilicone rubber compound KE-571-U (Shin-Etsu Chemical Co., Ltd.,containing the majority of vinyl-containing dimethylpolysiloxane with adegree of polymerization of about 5,000, up to 40% of dry silica with aBET specific surface area of 200 m²/g, and up to 10% ofsilanol-endcapped dimethylsiloxane oligomer with a molecular weight ofup to 700 as a silica dispersant, the compound being free of phenyl),adding thereto 0.5/2.0 parts of addition or hydrosilylation reactionvulcanizing agent C-25A/B (Shin-Etsu Chemical Co., Ltd.), and milling ona two-roll mill. The composition was calendered onto an embossed PETfilm of 100 m thick to form a layer of 0.7 mm thick, and continuouslyheat cured in a heating furnace at 140° C. for 10 minutes, obtaining asheet comprising a rubber base layer disposed on PET film.

A PSA layer was formed from a PSA composition. Specifically, the PSAcomposition was prepared by feeding into an agitation mixer 75 parts ofdimethylvinylsiloxy-endcapped dimethylpolysiloxane (1) having an averagedegree of polymerization of 1,000, and a 50% toluene solution containing25 parts of resinous copolymer (2) which is solid at room temperature(25° C.) and consists of (CH₂═CH)(CH₃)₂SiO_(1/2) units, (CH₃)₃SiO_(1/2)units and SiO₂ units wherein a molar ratio[{(CH₂═CH)(CH₃)₂SiO_(1/2)+(CH₃)₃SiO_(1/2)}/SiO₂] is 0.85 and aCH₂═CH-content is 0.0008 mol/g, mixing the contents for 30 minutes, andfully distilling off the toluene. To 100 parts of the resulting siliconerubber base were added 0.9 part of resinous copolymer (4) composedmainly of (CH₃)₂HSiO_(1/2) units and SiO₂ units and having SiH groups,with a SiH content of 0.0090 mol/g as a crosslinker and 0.05 part ofethynyl cyclohexanol as a reaction regulator. Agitation was continuedfor 15 minutes. The resulting silicone rubber composition was combinedwith 0.1 part of a platinum catalyst (Pt concentration 1%), yielding thePSA composition.

The PSA composition was coated on the rubber base layer to a thicknessof 1.0 mm using a comma coater, and heat cured in a heating furnace at140° C. for 10 minutes, yielding a two-layer cured laminate sheet. Therubber base had a JIS A hardness of 70, and the PSA layer had an Asker Chardness of 15.

The base side PET film was peeled from the laminate sheet, leaving awaterproof sheet which was evaluated by several tests to be describedlater. The results are shown in Table 1.

In a waterproof test, the waterproof sheets of 30 cm wide by 100 cm longwere serially applied along the boundary between an outdoor tank and apedestal as shown in FIG. 6. A sealant, Sealant Master 300, was appliedto bond a 2 cm peripheral portion of the waterproof sheet to the tank orpedestal. The structure was exposed to weather for a certain period (1month, 1 year).

Example 2

A rubber base layer was formed from a transparent uncrosslinkeddimethylsilicone rubber compound. Specifically, a dimethylsiliconerubber composition was prepared by providing 100 parts of a millabledimethylsilicone rubber compound KE-571-U (Shin-Etsu Chemical Co., Ltd.,containing the majority of vinyl-containing dimethylpolysiloxane with adegree of polymerization of about 5,000, up to 40% of dry silica with aBET specific surface area of 200 m²/g, and up to 10% ofsilanol-endcapped dimethylsiloxane oligomer with a molecular weight ofup to 700 as a silica dispersant, the compound being free of phenyl),adding thereto 0.5/2.0 parts of addition or hydrosilylation reactionvulcanizing agent C-25A/B (Shin-Etsu Chemical Co., Ltd.), and milling ona two-roll mill. The composition was sheeted by calendering onto anembossed PET film of 100 m thick to form an unvulcanized layer of 1.5 mmthick.

A PSA layer was formed from a PSA composition. Specifically, the PSAcomposition was prepared by feeding into an agitation mixer 50 parts ofdimethylvinylsiloxy-endcapped dimethylpolysiloxane (1) having an averagedegree of polymerization of 1,000, a 50% toluene solution containingparts of resinous copolymer (2) which is solid at room temperature (25°C.) and consists of (CH₂═CH)(CH₃)₂SiO_(1/2) units, (CH₃)₃SiO_(1/2) unitsand SiO₂ units wherein a molar ratio[{(CH₂═CH)(CH₃)₂SiO_(1/2)+(CH₃)₃SiO_(1/2)}/SiO₂] is 0.85 and aCH₂═CH-content is 0.0008 mol/g, and a 50% toluene solution containing 25parts of resinous copolymer (3) which is solid at room temperature (25°C.) and consists of (CH₃)₃ SiO_(1/2) units and SiO₂ units wherein amolar ratio [(CH₃)₃SiO_(1/2)/SiO₂] is 0.75, mixing the contents for 30minutes, and fully distilling off the toluene. To 100 parts of theresulting silicone rubber base were added 0.9 part of resinous copolymer(4) composed mainly of (CH₃)₂HSiO_(1/2) units and SiO₂ units and havingSiH groups, with a SiH content of 0.0090 mol/g as a crosslinker and 0.05part of ethynyl cyclohexanol as a reaction regulator. Agitation wascontinued for 15 minutes. The resulting silicone rubber composition wascombined with 0.1 part of platinum catalyst (Pt concentration 1%),yielding the PSA composition.

The PSA composition was coated on the unvulcanized rubber basecomposition coating to a thickness of 1.5 mm using a comma coater, andheat cured in a heating furnace at 140° C. for 10 minutes, yielding atwo-layer cured laminate sheet. The rubber base had a JIS A hardness of70, and the PSA layer had an Asker C hardness of 10.

The base side PET film was peeled from the laminate sheet, leaving awaterproof sheet which was evaluated as in Example 1. The results arealso shown in Table 1.

Example 3

As in Example 1, a sheet comprising a rubber base layer of 0.7 mm thickdisposed on PET film was obtained.

A PSA composition was prepared by feeding into an agitation mixer 70parts of dimethylvinylsiloxy-endcapped dimethylpolysiloxane (1) havingan average degree of polymerization of 450, and a 50% toluene solutioncontaining parts of resinous copolymer (2) which is solid at roomtemperature (25° C.) and consists of (CH₂═CH)(CH₃)₂SiO_(1/2) units,(CH₃)₃SiO_(1/2) units and SiO₂ units wherein a molar ratio[{(CH₂═CH)(CH₃)₂SiO_(1/2)+(CH₃)₃SiO_(1/2)}/SiO₂] is 0.85 and aCH₂═CH-content is 0.0008 mol/g, mixing the contents for 30 minutes, andfully distilling off the toluene. To 100 parts of the resulting siliconerubber base were added 3.0 part of methylhydrogenpolysiloxane (5) havinga SiH group on side chain (i.e., on a siloxane unit midway the molecularchain) having a degree of polymerization of 60 and a SiH content of0.0055 mol/g as a crosslinker and 0.05 part of ethynyl cyclohexanol as areaction regulator. Agitation was continued for 15 minutes. Theresulting silicone rubber composition was combined with 0.1 part ofplatinum catalyst (Pt concentration 1%), yielding the PSA composition.

As in Example 1, a two-layer cured laminate sheet was obtained. The PSAlayer had an Asker C hardness of 30.

The base side PET film was peeled from the laminate sheet, leaving awaterproof sheet which was evaluated as in Example 1. The results arealso shown in Table 1.

Example 4

As in Example 1, a sheet comprising a rubber base layer of 0.7 mm thickdisposed on PET film was obtained.

A PSA composition was prepared by feeding into a planetary mixer 60parts of dimethylvinylsiloxy-endcapped dimethylpolysiloxane (1) havingan average degree of polymerization of 300, 40 parts of resinouscopolymer (3) which is solid at room temperature (25° C.) and consistsof (CH₃)₃SiO_(1/2) units and SiO₂ units wherein a molar ratio[(CH₃)₃SiO_(1/2)/SiO₂] is 0.75, and 8 parts of hydrophobized fumedsilica having a BET specific surface area of 110 m²/g (R-972 by NipponAerosil Co., Ltd.) as finely divided silica, mixing the contents for 30minutes, and milling once on a three-roll mill. To 100 parts of theresulting silicone rubber base were added 0.99 part ofmethylhydrogenpolysiloxane (5) having a SiH group on side chain (i.e.,on a siloxane unit midway the molecular chain) with a degree ofpolymerization of 20 and a SiH content of 0.0060 mol/g as a crosslinkerand 0.05 part of ethynyl cyclohexanol as a reaction regulator. Agitationwas continued for 15 minutes. The resulting silicone rubber compositionwas combined with 0.1 part of platinum catalyst (Pt concentration 1%),yielding the PSA composition.

As in Example 1, a two-layer cured laminate sheet was obtained. The PSAlayer had an Asker C hardness of 40.

The base side PET film was peeled from the laminate sheet, leaving awaterproof sheet which was evaluated as in Example 1. The results arealso shown in Table 1.

Example 5

As in Example 1, a sheet comprising a rubber base layer of 0.7 mm thickdisposed on PET film was obtained.

A PSA composition was prepared. To 100 parts of the silicone rubber baseobtained as in Example 1 were added 0.5 part of resinous copolymer (4)composed mainly of (CH₃)₂HSiO_(1/2) units and SiO₂ units and having SiHgroups, with a SiH content of 0.0090 mol/g as a crosslinker, 1.5 partsof methylhydrogenpolysiloxane (5) having a SiH group on side chain(i.e., on a siloxane unit midway the molecular chain) with a degree ofpolymerization of 60 and a SiH content of 0.0055 mol/g as a crosslinker,and 0.05 part of ethynyl cyclohexanol as a reaction regulator. Agitationwas continued for 15 minutes. The resulting silicone rubber compositionwas combined with 0.1 part of platinum catalyst (Pt concentration 1%),yielding the PSA composition.

As in Example 1, a two-layer cured laminate sheet was obtained. The PSAlayer had an Asker C hardness of 20.

The base side PET film was peeled from the laminate sheet, leaving awaterproof sheet which was evaluated as in Example 1. The results arealso shown in Table 1.

Comparative Example 1

A commercially available butyl rubber based PSA sheet of the same sizeas in Example 1 was applied as in Example 1.

Tests Pressure-Sensitive Adhesion

The waterproof sheet was cut into samples of 25 mm wide by 10 cm long.According to JIS Z0237, the sample was attached to a 4-mm thick plate ofglass FL2.0 (Nippon Sheet Glass Co., Ltd.) which had been degreased withalcohol and air dried, with the PSA layer in contact with the glassplate. A bond strength was measured by peeling the PSA layer from theglass plate at room temperature, a rate of 300 mm/min, and an angle of180°.

Long-Term Attachment Stability

As above, the waterproof sheet sample of 25 mm wide by cm long wasattached to a 4-mm thick glass plate, with the PSA layer in contact withthe glass plate. The assembly was stored at room temperature and ahumidity of 50% RH for one month. A bond strength was then measured bypeeling the PSA layer from the glass plate at room temperature, a rateof 300 mm/min, and an angle of 180°.

Re-Peeling

As above, the waterproof sheet sample of 25 mm wide by cm long wasattached to a 4-mm thick glass plate, with the PSA layer in contact withthe glass plate. The assembly was stored at room temperature and ahumidity of 50% RH for one month. The PSA layer was peeled from theglass plate at room temperature, a rate of 300 mm/min, and an angle of180°. It was examined whether or not any sticky component wastransferred to the glass surface. The sample was rated NG whentransferred or OK when not transferred.

Elasticity to Deformation

The waterproof sheet was bent 180° whereupon it was examined whether ornot the sheet was damaged. The sample was rated OK when the sheet wasintact or NG when cracked and deformed.

Waterproofness

Initial waterproofness was evaluated after one month of weathering andrated OK for no rainwater entry or NG when rainwater entry was found.

Long-term waterproofness was evaluated after one year of weathering andrated OK for no rainwater entry or NG when rainwater entry was found.

TABLE 1 Comparative Example Example 1 2 3 4 5 1 Bond strength 3.1 4.63.3 3.1 3.2 0.2 (N/25 mm) Long-term attachment 3.0 3.5 3.3 3.0 3.3 0.1stability (N/25 mm) Re-peeling OK OK OK OK OK OK Elasticity to OK OK OKOK OK OK deformation Initial waterproofness OK OK OK OK OK OK Long-termOK OK OK OK OK NG waterproofness

Japanese Patent Application No. 2011-077757 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A waterproof sheet comprising a rubber base and a pressure-sensitiveadhesive layer disposed thereon, the adhesive layer comprising apressure-sensitive adhesive silicone resin or gel.
 2. The waterproofsheet of claim 1 wherein the rubber base is formed of silicone rubberhaving a hardness of 10 to 90 on JIS A scale.
 3. The waterproof sheet ofclaim 1 wherein the pressure-sensitive adhesive layer is formed of acured product of an addition cure silicone rubber composition, saidaddition cure silicone rubber composition comprising (A) 20 to 100 partsby weight of an organopolysiloxane containing at least twosilicon-bonded alkenyl groups in a molecule, having the averagecompositional formula (1):R¹ _(a)SiO_((4-a)/2)  (1) wherein R¹ is each independently a substitutedor unsubstituted monovalent hydrocarbon group of 1 to 10 carbon atoms,and a is a positive number of 1.5 to 2.8, (B) 0 to 80 parts by weight ofa resinous copolymer predominantly comprising R₃SiO_(1/2) units and SiO₂units, a molar ratio of R₃SiO_(1/2) units to SiO₂ units being in a rangeof 0.5 to 1.5, wherein R is a substituted or unsubstituted monovalenthydrocarbon group, and R contains alkenyl in a total amount of at least0.0001 mol/g, the total amount of components (A) and (B) being 100 partsby weight, (D) an organohydrogenpolysiloxane containing at least twosilicon-bonded hydrogen atoms in a molecule in an amount of 0.5 to 30parts by weight relative to 100 parts by weight of components (A) and(B) combined, the amount being such that a molar ratio of silicon-bondedhydrogen in component (D) to silicon-bonded alkenyl group in components(A) and (B) is in a range of 0.2 to 1.5, and (E) a catalytic amount ofan addition reaction catalyst, the cured product having surfacepressure-sensitive adhesion.
 4. The waterproof sheet of claim 3 whereinsaid addition cure silicone rubber composition further comprises (C) aresinous copolymer predominantly comprising R′₃SiO_(1/2) units and SiO₂units, a molar ratio of R′₃SiO_(1/2) units to SiO₂ units being in arange of 0.5 to 1.5, wherein R′ is a substituted or unsubstitutedmonovalent hydrocarbon group, and R′ does not contain or containsalkenyl in a total amount of less than 0.0001 mol/g, in an amount of 0to 400 parts by weight relative to 100 parts by weight of components (A)and (B) combined, the amount being such that a molar ratio ofsilicon-bonded hydrogen in component (D) to silicon-bonded alkenyl groupin components (A), (B), and (C) is in a range of 0.32 to 0.75 whencomponent (C) contains alkenyl.
 5. The waterproof sheet of claim 1wherein the pressure-sensitive adhesive layer has a hardness which islower than that of the rubber base and in a range of 1 to 60 on Asker Chardness scale.
 6. The waterproof sheet of claim 1 wherein thepressure-sensitive adhesive layer has a bond strength of 0.5 to 10 N/25mm to glass.
 7. The waterproof sheet of claim 1 wherein the rubber basehas a thickness of 0.2 to 5 mm and the pressure-sensitive adhesive layerhas a thickness of 0.3 to 3 mm.
 8. The waterproof sheet of claim 1 whichis applied to the boundary between an outdoor tank and a concretepedestal for waterproof treating the outdoor tank.
 9. A method ofwaterproof treating an outdoor tank rested on a concrete pedestal,comprising applying the waterproof sheet of claim 1 across an externallyexposed boundary between the tank and the pedestal, with thepressure-sensitive adhesive layer of the waterproof sheet being attachedto the tank and the pedestal.
 10. The method of claim 9 wherein thepressure-sensitive adhesive layer of the waterproof sheet is directlyattached to the tank and the pedestal without a primer.
 11. The methodof claim 9, further comprising applying a sealant around the waterproofsheet.
 12. The method of claim 11 wherein the sealant is applied alongthe outer periphery of the pressure-sensitive adhesive layer of thewaterproof sheet to form a sealing layer at the outer periphery of thepressure-sensitive adhesive layer.
 13. The method of claim 9 wherein thesealant is a silicone sealant.